Narendra Modi has for the first time publicly acknowledged his wife drawing an instant taunt from Congress leader Digvijay Singh and strong defence from his brothers, who described the marriage as a "social formality".

BJP's prime ministerial candidate acknowledged his marriage to Jashodaben for the first time in his affidavit filed along with his nomination papers in Vadodara Lok Sabha constituency yesterday. In the state assembly polls, he had left blank the column about spouse.

Congress General Secretary Digvijay Singh tweeted, "Modi accepts his marital status. Can women of this country trust a man who stalks a woman, deprives his wife of her right? Vote against Modi."

In the column in the affidavit about his wife's assets and liabilities, Modi has written that he has no information.

Jashodaben, a 62-year-old retired teacher, and Modi were married very young and had also separated because he moved out of home as a young RSS pracharak.

Singh's reference to stalking of a woman is an apparent reference to the surveillance of a woman by the Gujarat police

Allegedly at the behest of higher ups in the state government.

Seeking to contain the controversy, Modi's elder brother Somabhai said the marriage should be seen as a "social formality" which happened nearly 50 years ago.

In a statement sent to the media by the BJP, Somabhai said, "Our parents had not studied much and we were a poor family. To them Narendra was like any other child. In such context our parents conducted his marriage in a tender age with Jashodaben, but it turned out to be just a social formality for the sake of it."

"Modi, after leaving the house has not kept any contact with the family," Somabhai said, adding, "Service to the nation was his only religion. So he left home and material pleasures. His marriage was just a formality as he left the house soon after his marriage.

"Even Jashodaben has been living at her father's home and spending her life working in the education sector," Somabhai said.

"The incident (Modi's marriage) which had occurred 45-50 years ago is to be seen in the background of a poor and traditionally orthodox family," he said.

Somabhai said that Narendra Modi's current status should not be evaluated on the basis of "an incident" that had occurred 45 to 50 years ago.

Praising his younger brother, he said, "Narendrabhai was different amongst the six siblings. His interest in the service to the nation was quite apparent to us.

"But nobody could have estimated the intensity of his idea of service to the nation. He was also very influenced with the sacrifice and dedication of Swami Vivekananda and Lord Gautam Buddha."

Somabhai said that his younger brother had left the house and the family because he believed in the concept of 'world is a family'.

Modi's family members did not know much about him as he has never maintained active contact with them after he left the house, he said.

In his yesterday's affidavit Modi has stated that he has no information about the assets and liabilities of his wife.

His another brother Prahlad said that Modi has never denied that he is a married man and in the earlier election forms he had kept the column of wife blank.

"He has never denied it (marriage). In the earlier election (affidavits) the column (about spouse) would have been left blank due to some reasons. Whether he did it intentionally or not that is his personal issue," Modi's Prahlad said.